This invention relates generally to a hand operated dispenser having a snap-fitted, internally threaded closure cap for mounting the dispenser on the neck of the container of fluid to be dispensed. More particularly, the threaded closure cap is prevented from loosening after being tightened on the container.
The present invention comprises on improvement over U.S. Pat. No. 4,361,256 disclosing a threaded closure cap snap-fitted to the dispenser body for mounting the body to a threaded container neck. The lower end of the dispenser body has an external annular flange, and the closure cap has a flexible conical skirt in snap-fitting engagement with the flange for positively retaining the body and the cap together. On tightening the closure on the container neck, i.e., "torquing down", the flexible conical skirt on the cap deforms to some extent to enhance the tight seal between the body and the container neck, and to improve upon the tight engagement between the cap and the lower portion of the pump body. A gasket seal may be interposed between the lower end of the pump body and the upper end of the container neck which may be slightly compressed as the closure cap is tightened down.
Problems have been uncountered in the use of such a snap-fitted closure cap in that after assembling the dispenser body to the container, the tightened closure cap tends to back-off or loosen especially during shipment and storage thereby causing leakage of product from the container. For example, vibrations during shipment can cause the closure cap to loosen as the compressed gasket seal slips and relaxes. Likewise, should the pump body reorient itself on the container during shipment or during handling prior to shipment, torque back-off has been experienced upon turning movement of the dispenser body about the central axis of the container in a loosening direction. Moreover, during use of the dispenser, it may be necessary to reorient the dispenser body relative to the container such that, if turned in a loosening direction, the closure cap tends to back off causing leakage.